JPH02269854A - Production of bulky nonwoven fabric - Google Patents

Abstract

PURPOSE:To obtain the title sufficiently bulky and uniform product in producing nonwoven fabric by spun bond method by specifically treating web prepared by piling conjugate fiber bundle on a net conveyor before heating the web. CONSTITUTION:First, a conjugate fiber bundle 2 delivered from a spinneret 1 is sprayed on a net conveyor 4 by suction force of high-speed air flow from a device 3 and spraying air is sucked and removed from the bottom of the net conveyor 4 by an exhaust device 8 to pile the conjugate fiber bundle 2 on the net conveyor 4. Then the prepared web 5 is sprayed with an air flow from the bottom of the net conveyor 4 in such an intensity that the web 5 is floated 0.2-30mm from the net conveyor 4 at an air blowing part 9 between the spraying part of the conjugate fiber bundle 2 and a heating part of web and the web 5 is heat-treated by a furnace 6 to give the aimed product 7.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a bulky nonwoven fabric. More specifically, it relates to a method for producing a bulky nonwoven fabric suitable for the surface material of disposable diapers, interlining for clothing, cotton padding, etc. (Prior Art) Recent years A spunbond method has been developed and industrialized in which fiber bundles discharged from a spinneret are pulled and drawn by high-speed air currents, deposited on a net conveyor to form a web, and then heat-treated to produce nonwoven fabrics. In order to obtain a non-woven fabric, there is a method of heat-treating a conjugate fiber web with latent crimp properties to generate crimps (Japanese Unexamined Patent Publication No. 1471/1983), or a method of using composite fibers with actual crimps (Japanese Unexamined Patent Publication No. 1471-1971). Kaisho 63-282350
Publication No.) etc. are known. In order to obtain a nonwoven fabric with less unevenness in area weight using the spunpond method, it is necessary to prevent the deposited web from being disturbed or blown away by high-speed airflow reflected from the top surface of the net conveyor. For this reason, an exhaust device is installed below the web spraying part of the net conveyor.
A method is used in which substantially all of the airflow is passed through a net conveyor and sucked out. [Problems to be Solved by the Invention] As a result of being pressed against the net conveyor, the web is conveyed to the next process in a state where it is bitten by the net. Therefore, when attempting to make a bulky nonwoven fabric using latent crimpable fibers, the fibers get entangled with the net conveyor during the heat treatment process to generate curling S, inhibiting the occurrence of crimp, and resulting in insufficient bulking. It is easy to cause defects such as shrinkage spots (density spots) on the web, and even the mesh pattern of the net conveyor on the back side of the nonwoven fabric. Since these drawbacks affect the commercial value of low-weight, bulky nonwoven fabrics used as surface materials for disposable diapers, it is a major issue to resolve them.9.

[Means to solve the problem]

As a result of intensive studies to solve the above-mentioned problems of the prior art, the inventors of the present invention have found that the composite fiber bundle discharged from the spinneret is blown onto a net conveyor by the traction force of a high-speed air stream, and the air stream is directed from below the net conveyor. In a method for manufacturing a nonwoven fabric in which a web obtained by depositing by suction removal is then heat treated to cause crimp and bonding of fiber intersection points, the web is deposited in a region between a spraying section and a heating section. The present invention was completed after learning that the desired purpose could be achieved by blowing an airflow from the underside of the net conveyor with a strength of 0.2 to 30 m1 floating above the net conveyor. The invention will be further explained with reference to the drawings. FIG. 1 is a schematic diagram of a nonwoven fabric manufacturing apparatus used in the method of the present invention. Using two extruders (not shown), 2811 type thermoplastic resin is supplied to a composite spinneret (1), and the spun composite fiber bundle (2) is passed through a high-speed airflow traction device (3). It is pulled, sprayed onto a net conveyor (4), and deposited to form a web (5). Web (5) is the net conveyor (
4), the composite fibers are transported into a heating furnace (6) and subjected to heat treatment, and the composite fibers are crimped and the contact points of the fibers are fixed by the fusion of the low melting point component, forming a nonwoven fabric (7). In the present invention, an exhaust system R (8) is provided below the net conveyor (3) at the position where the fiber bundle (2) is sprayed.
) by suctioning away most of the high-speed airflow.
Kuep (5) is brought into close contact with the Wone Net conveyor (4) to stabilize its shape. Next, the web (5) is heated to a heating furnace (6).
Nine airflow blowing devices installed at the position before reaching K (9)
The web (5) is moved from the net conveyor (4) by 0.2
Net conveyor (4) so that ~30fi floats
Blow air from below. When the floating height is less than 0.2M, the fibers on the lower surface of the web (5) are removed from the net conveyor (4).
), the web shrinks incompletely during the heat treatment process, resulting in a nonwoven fabric with poor bulkiness, or a nonwoven fabric with uneven fabric weight due to uneven shrinkage or a net conveyor mesh pattern. Also, the floating height is 30fi?
If it is too long, the entanglement of the fibers in the quep becomes loose and the shape of the web becomes unstable, making it impossible to obtain a homogeneous nonwoven fabric. The airflow spraying device (9) may be any device as long as it can spray a desired amount of airflow evenly over the entire width of the web.
1), one with a slit-shaped nozzle (2-2), and one with such nozzles arranged in multiple stages in the length direction of the web (
2-3] It is a schematic diagram of the 4th voice. As the high-speed airflow traction device (3), any known device used in general spunbonding methods can be used. i! as a heating furnace (6) An infrared heater or a device using hot air as a heat source is preferable because it does not inhibit the occurrence of fiber crimp due to heat treatment. A thermal calendar roll is not preferred because it impairs the bulkiness of the nonwoven fabric. The heating furnace (6) shown in FIG. 1 is a schematic diagram in which far-infrared heaters are provided in two stages. The composite fiber used in the ninth step to obtain the bulky nonwoven fabric in the present invention is
Two or more thermoplastic resins with melting points different by 10°C or more, preferably 15°C or more are composite-spun into a parallel type, sheath-core type, or sea-island disk type so that the resin with a low melting point occupies the majority of the fiber surface. be. By selecting the heat treatment conditions in the heating furnace, such composite fibers can be crimped and only the low melting point resin can be melted to fix the contact points of the fibers, making it possible to create bulky and strong sterile fabrics. can get. Examples of such thermoplastic resin combinations include crystalline polypropylene/high-density polyethylene, crystalline polypropylene/
Ethylene vinyl acetate copolymer, polyethylene terephthalate/high density polyethylene, nylon 66/nylon 6
etc. The number of crimps generated by heat treatment is 4 to 60/
25 fi, fiber thickness of 0.1 to 15 deniers can be selected as appropriate depending on the purpose of the nonwoven fabric, and the density of the obtained nonwoven fabric is 0.005 to 0.02 f for use as a stuffing material for clothing.
/cd. For surface material applications of sanitary materials, 0.01 to (105 f/d,
When used as interlining for clothing, it can be controlled over a wide range, such as 0.04 f/d or more. (Example) The present invention will be explained in more detail with reference to Examples.
The methods for measuring physical property values used in these Examples are as follows. Measure the fabric weight (C9/vl) and thickness (3) of five square sample pieces of density: 20cNX201, calculate the ratio x'i using the following formula, and display the entire average value. Ratio x<y7ci)=, basis weight/thickness XIo, 000 strength・
Elongation: According to the method for measuring "tensile strength and elongation" of JIS L 1085 (Testing method for non-woven fabric interlining), 5 test pieces of 5CIIX203 were taken in the vertical and horizontal directions of the sample, and the grip interval was 10clI. , tensile speed 3 Q
The cutting strength (Ag15m) and elongation rate (%) are measured under the conditions of cm/mid, and the average value is displayed. Example 1 Crystalline polypropylene (
MFR22; JIS K 7210. Condition 1 in Table 1
4) of the other extruder is quantitatively supplied to a parallel type composite spinneret with 198 holes at a high min. 2.
Using the 0201n/zln high-speed airflow traction device,
It was sprayed onto a net conveyor moving at 11.5 Fff/min. An exhaust device installed below the location where the fiber bundles are blown on the net conveyor sucks and removes the blown air and fixes the web on the net conveyor.Before the web reaches the heating furnace, an airflow blowing device removes the blown air. was sprayed from the underside of the net conveyor to float the web approximately 3 IIJ. As an airflow blowing device,
Three pipes each having a large number of pore nozzles as shown in FIG. 2 (2-1) were arranged in the direction of web movement. Next, the first stage of the web gold was heated to 140°C, and the second stage to 150°.
After being heat-treated by passing through a far-infrared heater heating furnace adjusted to C for 70 seconds, the nonwoven fabric was left to cool. In addition, this composite fiber has 24 pieces/25 f due to this heat treatment.
1 spiral crimp occurred. In this nonwoven fabric, the contact points of the composite fibers are fixed by fusion of high-density polyethylene, and the basis weight is 23 f/Wl. Thickness 1.53jlll, density 0.015 f/cl,
Strength (vertical direction 2,450 da 153, horizontal direction 1.51
0f153), elongation (fc direction 70%, horizontal direction 46%
%), there were no wrinkles or mesh patterns on both the front and back surfaces, and the nonwoven fabric was homogeneous and suitable as a surface material for disposable diapers. Example 2 Using the same apparatus 11 as in Example 1, polyethylene terephthalate (intrinsic viscosity 0.65) extruder (B) was produced from the extruder shell.
From is cotton-like low density polyethylene (MFR20: JIS
K7210. 40g/each of condition 4) in Table 1
Composite spinning is carried out by supplying at min.
m/min, net conveyor speed 6.8 m/m
in, the floating height of the web is approximately 8 WIM, and both the front and rear stages are 1
A nonwoven fabric was obtained by heat treatment in a heating furnace at 42'C for 2 minutes. In addition, this composite fiber can be reduced to 20 pieces/25mm by this heat treatment.
1 spiral crimp occurred. This nonwoven fabric has a basis weight of 40 f/m, a thickness of 2.35 n, a density of 0.01711/cd, and a strength (fc 'C direction of 5.86
011156M, horizontal direction 8,260g 15cm elongation (
47% in the vertical direction and 44% in the horizontal direction), and was homogeneous with no wrinkles or mesh patterns on both the front and back surfaces, making it suitable as an intermediate material for disposable diapers or as an interlining for clothing. Example 3 Crystalline polypropylene (MFR21) from extruder (4)
? , co-merged polypropylene (MFR) from the extruder (B)
II, propylene 92 wt%, ethylene 8.5 wt%
A nonwoven fabric was obtained under the same conditions as in Example 1, except that 14.5 wt %) of butene was supplied and the total flying height of the web on the net conveyor was 5 u. Under these conditions, 36/25 spice rings were generated in the composite fiber. The nonwoven fabric obtained here has a basis weight of 2
6 f/door, thickness 2. Off, density 0.013 fl/
d, strength (2.410 f/15 cll in the vertical direction, 1.4301/5 apt in the horizontal direction), and elongation (36% in the vertical direction, 32% in the horizontal direction), with no wrinkles or mesh patterns on both the front and back surfaces. It is homogeneous and suitable as a surface material or intermediate material for disposable diapers). Comparative Example 1 A nonwoven fabric was obtained under the same conditions as in Example 1, except that the web deposited on the net conveyor was not blown with air from the airflow blower and was floated off. This non-woven fabric has a serrated 21y/g, thickness 0.81111, density 0.026 f/c4. Strength (vertical direction 8.020f
/15ex, 1.930 f15tM in the horizontal direction) and elongation (63% in the vertical direction, 32% in the horizontal direction), the front surface had slight wrinkles, and the back surface had a net conveyor mesh pattern in some places. Although this nonwoven fabric has high strength, it has poor bulkiness and is non-uniform, so it cannot be used as a surface member for disposable diapers. [Effect] According to the present invention, the economic efficiency of the spunbond method k <4f. It is possible to obtain a bulky and homogeneous lightweight nonwoven fabric while maintaining the same properties.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a nonwoven fabric embroidery device used in the method of the present invention, and FIG. 2 is a schematic diagram of an air stream blowing device. that's all

Claims (1)

[Claims] (1) The composite fiber bundle discharged from the spinneret is blown onto a net conveyor by the traction force of a high-speed air stream, and the air stream is suctioned and removed from the underside of the net conveyor to deposit the resulting web, which is then heat-treated. In a method for manufacturing a nonwoven fabric in which crimp occurs and fiber intersections are bonded by
A method for producing a bulky nonwoven fabric, characterized by blowing airflow from the underside of a web conveyor with such strength that the web floats 0.2 to 30 mm above the web conveyor.